Hmmmmmm.
I'm not sure of comparing non-Orthodox Sacraments to adultery. I suppose there is somewhat a picture there, but I've never heard anyone explain it that way.
Rather than some kind of metaphor, I prefer the way I have always heard it explained. The Sacraments are administered by the Church, and are a way of us sharing communion with one another. All Sacraments - baptism, the Eucharist, Confession, holy matrimony. If we receive a sacrament somewhere other than the Orthodox Church, by our actions we are in effect uniting ourselves to that body. And since we are not in full communion with non-Orthodox churches, that is in essence choosing to separate ourselves from the Church. We excommunicate ourselves by our actions. This can always be healed by Confession - one can always renter the Church.
No one should ever be barred from communion for offending the Church. People are barred for removing themselves. We don't excommunicate except in extremely serious circumstances - like someone teaching publicly that Christ was not divine, and continuing to do so after being warned. In fact, it is a complaint made against the Church that she gives so much space for repentance and doesn't quickly excommunicate people, even when they fall into serious error.
A person can be told to refrain from communion because of a serious sin, like having killed someone. It is not a punishment though, but giving space for repentance. Everything, everything we do is aimed at healing the person from sin, and great pastoral care should be taken in this effort. It is possible if a priest has told someone to refrain from communion, that after a time, they speak to the priest, if he feels the time spent has achieved the work necessary for the soul, he can lift the rest of the time and readmit them to receive the Eucharist again.